Refinement of magnesium from molten salts using furnaces is well known in the art.
U.S. Pat. No. 5,167,700 discloses a method and apparatus for refining magnesium, using a melt composition rich in calcium chloride with a content of calcium fluoride.
Electric furnaces for the continuous refining of magnesium are disclosed in Canadian Patent No. 1022978.
U.S. Pat. No. 4,385,931 describes an improved method for the continuous refining of magnesium by the precipitation of impurities in the form of sludge, and a refining furnace for carrying out the method.
Magnesium refining today is mostly carried out from a melt placed in a suitable furnace. After a period of time, the mixture is allowed to stand to let the impurities settle down as a sludge at the bottom of the furnace. The refined magnesium collects in the upper part of the furnace.
Barium chloride, a common additive to molten salts for weightening the same, is toxic, therefore working with it is potentially dangerous and needs to be done with much precaution and under safety systems. When barium chloride is used as an additive to molten salts for refinement, it is necessary to remove sludge and salts from the refining equipment. Removal and treatment of barium-containing waste is also problematic and expensive.
Another additive commonly used in weightening molten salts is calcium chloride. The density of this salt compared to barium chloride is low. Therefore, larger quantities of calcium chloride are needed for equal weightening than barium chloride.
The art therefore has so far failed to provide weightening compositions which overcome the aforesaid drawbacks.